Safety guards are typically provided over the cutter heads on woodworking power tools such as jointers/planers and other power tools. However, most guards are easily rotated open during operation of the tool in a manner which can expose the high-speed cutter blade beyond the edges of the work piece to possibly inflict injury on the operator. A power tool such as a jointer/planer typically includes a work surface which may be provided by separate but adjoining tables, a jointer/planer cutting tool head projecting at least partially through the work surface, for example, between the separate tables, a fence projecting upwardly from the work surface on a first side of the tool head and safety guard mounted on an opposing, second side of the head for movement from an initial position adjoining the fence and covering the tool head to a working position spaced from the fence and partially exposing the tool head to the work piece.
In the most common form of mounting, the guard is pivotally supported on the second side of the tool head and biased by suitable means such as one or more springs towards the fence so as to cover the tool head. The work piece is passed between the pivot and the fence. When the work piece strikes the guard, the guard rotates sufficiently away from the fence to expose the cutting tool head to the work piece. However, if the workman passes his fingers between the pivot and the fence on the side of the work piece adjoining the work surface, the workman's fingers are exposed to and can be cut by the head.
While a number of patents disclose various stop devices for cutter tool guards, most such devices are designed to stop the guard from striking the fence after being released by the work piece. These include, for example, U.S. Pat. Nos. 2,099,519, 2,123,627 and 2,747,628. Such devices provide no protection against opening of the guard to expose a portion of the cutting tool head along the side of the work piece where the operator's hand may be positioned.
U.S. Pat. No. 2,895,517 to Rhett discloses a finger guard mechanism for jointers. The mechanism includes a guard mounted on a swingable arm and held against the fence and work piece by springs. The mounting permits linear movement of the guard across the table towards and away from the fence. An adjustable limit stop is provided through a hinged knuckle coupled with the swingable arm. The guard further includes a plurality of spring loaded pins which are retracted by the work piece when the work piece is passed over the blade and which extend individually as the work piece passes each of them. The mechanism of Rhett is relatively complex involving multiple spring loaded arms supporting multiple spring loaded pins on a compound linkage. Not only would this device be expensive to manufacture and to properly install, it is not capable of being retrofitted onto power tools equipped with conventional, pivotally mounted safety guards.
The present invention resolves the problem of a simple, relatively inexpensive to manufacture and easy to install guard stop capable of being retrofitted or easily modified to retrofit into a variety of power tools using conventional, pivotally supported safety guards to control the permitted range of rotation of those guards to prevent exposing more of the cutting tool head than is necessary simply to pass a work piece between the guard and a fence of the tool.